1. Field of the Invention
The present invention relates to a static electricity chuck apparatus and a semiconductor producing apparatus having the static electricity chuck apparatus for absorbing and holding a semiconductor substrate which can be preferably applied to various film-forming processes, plasma etching processes, ion implantation processes, ion doping processes, and the like in production of a semiconductor device, and the invention also relates to a static electricity chuck apparatus and a semiconductor producing apparatus having the static electricity chuck apparatus which can control a temperature of a surface of an absorbed body and which has excellent heat transfer performance and durability, and which has high adhesion with respect to a work piece.
2. Description of the Related Art
Conventionally, in a producing process of a semiconductor device, static electricity chuck is used for holding a semiconductor substrate in a film forming apparatus for forming a thin film on the semiconductor substrate, an etching apparatus for making fine work, or an ion doping apparatus. In this static electricity chuck, an electrode is embedded in an insulating layer, its upper surface is defined as a holding surface of the substrate, direct current is applied between the electrode and the substrate placed on the holding surface so that absorbing force called Coulomb force by dielectric polarization or Johnson-Rahbeck force by fine leakage current is generated, and the substrate is absorbed and held by the holding surface.
According to Japanese Patent Application Laid-open No. 6-349938 for example, a wafer which is a work piece is absorbed and held by static electricity by a static electricity chuck sheet on a susceptor provided in a hermetic processing chamber. A wafer absorbing surface of the static electricity chuck sheet is provided with a plurality of gas supplying holes, inert gas such as He supplied from the gas supplying holes is dispersed into a gas dispersion groove formed between the static electricity chuck sheet and the wafer, and the gas is exhausted from an exhaust hole through a gas recovering groove formed in an outer periphery of the gas dispersion groove. By enhancing the specific thermal conductivity between the wafer and the static electricity chuck sheet, a temperature distribution difference of the wafer is suppressed, gas is prevented from leaking, and the wafer is processed with high precision.
According to Japanese Patent Application Laid-open No. 7-335630 for example, a gap between a wafer and a stage of a static electricity chuck having heating or cooling function is not set uniformly, and mixture gas comprising gas of excellent thermal conductivity and gas of inferior thermal conductivity such as He gas and Ar gas is introduced into the gap. By changing the mixture ratio of gases, a distribution of overall heat transfer coefficient between the wafer and the stage is changed and temperature distribution of the wafer is changed, or a contact surface or space between the wafer and the stage is divided into a plurality of regions, and temperature distribution of the wafer is changed by individually controlling gas pressure in each region. With this structure, the wafer is uniformly heated and cooled, the wafer temperature can be made uniform at the time of production of the semiconductor device, and a semiconductor device which is finer and has high performance can be produced.
As an electricity insulating layer of the static electricity chuck, it is proposed to use ceramic such as alumina and high polymer material such as polyimide and silicone rubber, and such an insulating layer has partially been brought into actual use as described in Japanese Patent Applications Laid-open No. 7-106300, No. 9-298233, No. 2000-113850, and No. 2000-286332.
According to the Japanese Patent Application Laid-open No. 7-106300, an exposing surface of the electricity insulating layer comprising high polymer organic film is coated with fluoroplastics to enhance the plasma resistance of the electricity insulating layer. According to Japanese Patent Application Laid-open No. 2000-113850, various ceramics or glasses are used for the electricity insulating layer, and the exposing surface is coated with silicone resin such as PFTE, methylphenyl vinyl and phlorosilicone, which has resistance to plasma and excellent heat resistance, chemical resistance and aging resistance, as anti-corrosive insulating film.
In Japanese Patent Application Laid-open No. 2000-286332, a metal conductive film is coated with a pair of insulating films such as polyimide resin film so that the conductive film is sandwiched from its opposite surfaces over the entire surface. An upper surface and all side surface of the chuck body obtained in this manner and a surface of a periphery of the chuck body of a mounting stage on which the chuck body is placed and fixed are coated with protecting film comprising tetrafluoride resin or trifluoride resin, and an exposing surface of the periphery of the chuck body of the mounting stage is further coated with a protecting ring.
With this structure, it is described that corrosion is not generated on the static electricity chuck and periphery of its mounting stage by any etching such as down flow-type etching and reactive ion etching, and life of the static electricity chuck apparatus is not shortened.
Japanese Patent Application Laid-open No. 9-298233 discloses a static electricity chuck in which an electrode is disposed on a first insulating layer comprising heat conductive silicone rubber on a metal support plate, a second insulating layer comprising heat conductive silicone rubber having hardness of 85 or lower and surface roughness of 5 xcexcm or lower is formed on the electrode to dissipate heat, adhesion between the electrode and the substrate is enhanced, contact thermal resistance is suppressed to lower level, and a temperature of the substrate is set uniformly and constantly with high precision.
According to Japanese Patent Application Laid-open No. 2000-113850, an electricity insulator of a static electricity chuck is made of silicone rubber, an electricity insulating film such as diamond-like carbon, fluoroplastics and polyimide, which has higher mold releasing performance than silicone rubber has, is formed on a surface of this electricity insulator made of silicone rubber, and separating performance of the wafer is enhanced without lowering heat transfer performance between the wafer and the static electricity chuck.
Moreover, according to Japanese Patent Application Laid-open No. 11-163109, the static electricity chuck constitutes a wafer holding apparatus which comprises a wafer holding base body whose upper surface of ceramic body having an inside electrode constituting a static absorbing electrode, a heater electrode, and plasma generating electrode is holding surface of the wafer; and a base body comprising a porous ceramic body whose thermal expansion difference between the wafer holding base body and the ceramic body constituting the wafer holding base body is 3xc3x9710xe2x88x926/xc2x0 C. or lower and having a pore into which metal is charged. The base body is bonded to a lower surface of the wafer holding base body through wax material mainly comprising aluminum, thereby constituting the wafer holding apparatus. Therefore, when the base body is bonded to a metal temperature control apparatus having cooling or heating function, it is possible to bond them strongly without deteriorating heat transfer characteristics of the bonded portions.
By the way, like the static electricity chuck disclosed in Japanese Patent Application Laid-open No. 11-163109, if the wafer holding surface is constituted by ceramic, the ceramic is obtained by sintering powder, and solids having high hardness come into contact with each other. Therefore, a gap as small as micro unit is generated in the contact surfaces between the wafer and the wafer holding surface, contact thermal resistance is increased, and since air in the gap disappears in vacuum environment, the contact thermal resistance is further increased, and the heat transfer performance is lowered.
The static electricity chuck disclosed in Japanese Patent Application Laid-open No. 7-335630 is accomplished to avoid the above-described deficiency caused when the wafer holding surface is held by the ceramic, inert gas such as He gas is supplied to the gap generated between the ceramic and wafer at the time of vacuum, thereby enhancing the heat transfer characteristics. For this purpose, however, it is necessary to install a gas supply apparatus, a structure of the entire apparatus is complicated and increased in size, and in order to supply two kinds of gases and to make the temperature distribution of the wafer uniform by controlling the gas supply region, the mechanism is further complicated, and it is impossible to make practical use of such an apparatus.
Meanwhile, like Japanese Patent Application Laid-open No. 9-298233, silicone rubber is used instead of ceramic, and heat conductive silicone rubber which has flexibility as low as hardness 85 or lower and has surface roughness of 5 xcexcm or lower is used as a second insulating layer which constitutes the wafer holding surface, thereby obtaining conformability with respect to the wafer and securing heat radiation characteristics, and the temperature distribution of the wafer is uniformed. However, the hardness of the silicone rubber is lowered and adhesion performance is increased, the wafer is less prone to be separated, and since anti-corrosion characteristics are inferior, durability is poor. Moreover, the silicone rubber has poor plasma resistance and durability, and it is difficult to actually use the silicone rubber for an etching apparatus and thus, the silicone rubber is limited to a partial usage such as an ion implantation apparatus.
According to the static electricity chuck of Japanese Patent Application Laid-open No. 2000-113850, to avoid the above-described deficiency caused by the adhesion of the silicone rubber, an electricity insulating film such as diamond-like carbon, fluoroplastics and polyimide which is easily released from mold is formed on a surface of the silicone rubber constituting the wafer holding surface, but it is not easy to form the insulating film made of such material, and attention is paid only to easiness of mold releasing operation with respect to a wafer and thus, a side surface is still exposed to processing atmosphere. Therefore, durability, especially durability in plasma atmosphere, can not be expected.
Further, in order to enhance the plasma resistance, if a surface of a static electricity chuck made of silicone rubber is coated with material having high hardness such as diamond-like carbon (DC), fluoroplastics, and polyimide, contact thermal resistance is adversely increased if the hardness of the chuck is increased to about the same as that of the silicone rubber, heat transfer performance can not be enhanced as expected. As a result, it is impossible to coat having sufficient thickness to withstand the plasma and in actuality, it is impossible to use it for the etching apparatus.
In the static electricity chuck apparatus of Japanese Patent Application Laid-open No. 2000-286332, a surface of an insulating parent material comprising polyimide resin is coated with a protecting film made of tetrafluoride resin or trifluoride resin, but compatibility between polyimide resin and fluoroplastics is low, and durability is poor even if they are bonded through adhesive.
The present invention has been accomplished in view of the above problems, and it is a concrete object to provide a static electricity chuck apparatus in which conformability between a holding surface of a work piece and the workpiece is enhanced at the time of various processing, the workpiece can be brought into intimate contact and held effectively without generating a gap therebetween, the workpiece can easily be separated from the holding surface, the heat transfer performance between the workpiece and the holding surface is enhanced, and corrosion resistance is excellent. Other objects will be apparent from the following explanation.
A basic structure of the present invention is a static electricity chuck apparatus in which an electrode is disposed in an insulating layer disposed on a metal support plate, and an upper surface of the insulating layer is absorbed and held by static electricity as a holding surface of an absorbed body, wherein the insulating layer disposed at least on an upper surface side of the insulating layer covering the electrode is made of viscous fluid or low hardness gel body.
If viscous fluid or gel body having low hardness is employed as a portion of the electricity insulating layer, it is possible to bring the substrate holding surface of the static electricity chuck into intimate contact with the back surface of the substrate uniformly, utilizing physical properties that the viscous fluid or gel body having low hardness is deformed in accordance with its mating material shape. It is possible to substantially eliminate a vacuum layer from the contact interface even under vacuum environment at the time of etching for example, and the contact thermal resistance is reduced and high heat conductivity is secured.
Here, examples of the viscous fluid are various grease and silicon oil having thermal conductivity of one or higher. Preferable material of the gel body is high polymer material, and preferable examples of the material are silicon gel, polyurethane gel and epoxy gel. Normal gelation of high polymer material is generated when crosslinkings are formed when monomers including multi-functional group generate condensation reaction or when high polymer dissolved matter generates intermolecular reaction by crosslinking agent, ionic bond and the like, or hydrogen bonds or hydrophobic bonds between solutes. The gel body in the present invention is not limited to material which is geleted and maintains a stable gel state, but the gel body may mainly comprise high polymer material whose phase is changed reversibly between solid phase and liquid phase depending upon peripheral condition.
It is preferable that a surface of the electrode is subjected to compatibility processing with respect to the insulating layer. For example, the adhesion performance between metal and the insulating layer made of vinilidene fluoroplastics is high as compared with other fluoroplastics, but in order to further enhance the adhesion, when aluminum electrode is used, for example, the surface of the electrode may be subjected to almite processing, and the surface of a copper electrode is subjected to trazine processing. By carrying out such surface treatment, it is possible to remarkably enhance the adhesion between resin, which mainly comprises vinilidene fluoride, and the electrode.
Preferably, the gel material having low hardness or viscous fluid is mainly made of high polymer material whose phase is changed reversibly between solid phase and liquid phase depending on peripheral conditions, and the gel material is semi-fluidized or fluidized when the absorbed body is absorbed, and the absorbed body is brought into intimate contact and held uniformly.
When the high polymer material is thermoplastic resin material, it is softened or melted at a temperature (softening point or melting point) inherent to the material, thus semi-fluidized or fluidized, and is solidified at a temperature lower than the said temperature. The softening point or the melting point is varied depending upon material, and the material may be burned or deteriorated depending upon the processing temperature in some cases. Or, physical properties may be changed depending upon electrical processing condition. Therefore, in the present invention, it is necessary to select the high polymer material taking into account the processing temperature or electromagnetic condition at the time of static electric absorption.
A preferable high polymer material is thermoplastic resin material, and examples of the material are hydrocarbon-based synthetic resin such as various polyethylene, polypropylene, polymethyl pentene, crystalline polybutadiene and isostatic polystyrene; condensation synthetic resin such as polyacetal, various polyamide, various polyterephthalate and polyvinyl alcohol; non-crystal synthetic resins such as polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, ethylene tetrafluoroethylene copolymer; line structure resin such as polyimide, polyamide imide and polyether ketone; and various plastic alloy.
Important points of the present invention are that resin material of the second insulating layer constituting the holding surface of the absorbed body at the time of the static adsorption is semi-fluidized or fluidized, and the insulating layer must be solidified at the non-processing time other than static adsorption time. For example, if a processing temperature at the time of static adsorption exceeds the softening point or melting point of the resin material, the second insulating layer is semi-fluidized or fluidized, deformed along the holding surface of the absorbed body with large freedom, and comes into intimate contact with the entire holding surface of the absorbed body without gap. If the processing is completed and a peripheral temperature becomes lower than the softening point or melting point of the resin material, the insulating layer is solidified.
In the present invention, it is necessary to pay attention also to the adhesion between the resin material and the absorbed body. If the adhesiveness is strong, the resin material is solidified adhering to the absorbed body after the processing, it becomes difficult to peel off the absorbed body from the absorbing surface, and the absorbed body may be damaged in some cases. Therefore, when the absorbing surface of the second insulating layer is directly made of high polymer material, material having poor adhesion strength with respect to other material such as polymethyl pentene is used. In this regard, since the melting point of the polymethyl pentene is 230xc2x0 C. to 240xc2x0 C., extremely high among high polymer material, it can withstand the high temperature processing with respect to the absorbed body.
If gel material of low hardness or viscous fluid is employed as a portion of the electricity insulating layer, it becomes possible to bring the substrate holding surface of the static electricity chuck into intimate contact with the back surface of the substrate, utilizing the physical properties that gel material of low hardness or viscous fluid deforms along the shape of the mating material. Thus, it becomes possible to substantially eliminate a vacuum layer from the contact interface even under vacuum environment at the time of etching, for example, and the contact thermal resistance is reduced and high heat conductivity is secured.
Here, examples of the viscous fluid are various grease and silicon oil having thermal conductivity of one or higher. Preferable material of the gel body is high polymer material, and preferable examples of the material are silicon gel, polyurethane gel and epoxy gel. Gelation of high polymer material is generated when crosslinkings are formed when monomers including multi-functional group generate condensation reaction or when high polymer dissolved matter generates intermolecular reaction by crosslinking agent, ionic bond and the like, or hydrogen bonds or hydrophobic bonds between solutes. The gel body in the present invention is not limited to material which is geleted and which maintain a stable gel state, and the gel body may mainly comprises high polymer material whose phase is changed between solid phase and liquid phase depending upon peripheral condition in a reversal manner. Among the above gel high polymer materials, silicon gel is most preferable because of the following excellent characteristics.
The basic structure of silicon gel consists of dimethyl siloxane polymer mutually crosslinking by chemical bonding, thereby silicon gel has intermediate characteristics between the silicone rubber and silicon oil, and is a much softer than rubber and is a material having shape-keeping characteristics.
Crosslink density of silicone gel is controlled to ⅓ to {fraction (1/10)} of normal silicone rubber. Further, there is no hydrogen bond between water molecule and polar group unlike general hydrogel, and the polymer skeleton is thermally stable, thus gel state is maintained in wide temperature range. Moreover, this silicon gel has following characteristics: 1) temperature dependency of physical properties is low and there is heat resistance, 2) mechanical strength is relatively high, 3) viscoelastic characteristics can be controlled and formation is easy, and 4) electrical characteristics and weather resistance are excellent.
The low hardness gel high polymer material used in the present invention need to have low hardness and low elastic modulus so that contact thermal resistance can be reduced, and it is preferable that JIS K6301 hardness is 10 or lower and JIS K2207 penetration number is 5 or higher, more preferably, 50 to 200.
If the thickness of the gel high polymer material is too thin, the mechanical strength and insulating damaging voltage are lowered, which is not always effective for reducing the contact thermal resistance. On the other hand, if it is too thick, the thermal resistance is increased correspondingly. According to an experiment, it was found that optimal value was obtained under certain thickness of the gel high polymer material. The thickness is preferably 0.1 to 2 mm. Especially when it is used as the static electricity chuck, since its absorbing force inversely proportional to square of thickness of the dielectric layer, it is preferable that the thickness is 1 mm or less.
When all the electricity insulating layer is made of gel body having low hardness, it is preferable that the gel body at this time is obtained by gelating the high polymer material as described above. In the static electricity chuck having electricity insulating layer of gel body alone as in the present invention, the electricity insulating layer has the shape-keeping characteristics and is extremely flexible and thus, if the substrate is placed and held, the holding surface of the electricity insulating layer is deformed along bumps and dips of the back surface of the substrate, as described above, and is brought into intimate contact over substantially entire surface. Therefore, the contact thermal resistance between the substrate and the absorbing surface can be suppressed to a low value. As a result, cooling efficiency is enhanced, a temperature of the substrate is controlled efficiently and precisely, and thus it is possible to lower the temperature of the substrate and to save energy of the cooling apparatus.
Further, according to the static electricity chuck, as described above, since it is possible to suppress the thermal resistance to an extremely low level, heat transfer performance is excellent even in vacuum, and heat-transfer cooling gas promoting, which is conventionally used, becomes unnecessary. In addition, gel material can provide higher heat conductivity if heat conductive filler is added. Examples of the heat conductive filler to be added to the gel material are alumina, aluminum nitride, boron nitride and silicon nitride.
It is preferable that the thermal conductivity is 1 W/mxc2x7K or higher, and an example of a sheet formed product of silicon gel is xcex gel (produced by GelTech, Inc.) (thermal conductivity 6.5 W/mxc2x7K).
On the other hand, examples of the electrode material are metal conductor such as copper, aluminum, nickel, silver and tungsten, and ceramic such as titanium nitride.
In the present invention, it is preferable that the insulating layer comprises at least two layers, at least one inner layer is made of gel body having low hardness or viscous fluid, and the outer exposing surface is coated with hardening film of energy beam hardening mordant.
This energy beam hardening mordant has excellent adhesion force with respect to the absorbed body before energy beam is radiated, but if the energy beam is radiated and the mordant is hardened, the adhesion force is extremely lowered. Thus, the absorbed body can easily be peeled off from the absorbing surface of the static electricity chuck.
As disclosed in Japanese Patent Application Laid-open No. 2000-129227, examples of acrylic mordant, which is one of main components of energy beam hardening mordant, are trimethylol propane triacrylate, tetramethylol methane tetraacrylate, pentaerythritol triacrylate, depentaerythritol triacrylate, 1,4-butylene glycol diacrylate, 1,6-hexane diol diacrylate and polyethylene glycol diacrylate. An example of energy beam polymer compound, which is another main component of energy beam hardening mordant, is urethane acrylate oligomer.
The present inventors studied about material of synthetic resin material suitable for an insulating layer of electricity chuck, wherein the resin, though it has never been used in the field of art, has excellent electric insulating characteristics, can secure adhesion with respect to the substrate, and can easily be separated from the substrate. As a result, the inventors found that as a synthetic resin material having such physical properties, a synthetic resin material resin comprising vinilidene fluoride as main component is optimal.
Examples of synthetic resin material resin comprising vinilidene fluoride as main component are copolymer between vinilidene fluoride and ethylene trifluoride, copolymer between vinilidene fluoride and propylene hexafluoride, and copolymer between vinilidene fluoride and perfluoro vinyl ether. These copolymers comprising vinilidene fluoride as main component can generate high dielectric even in non-roll and thus, production is easy, and absorbing force is excellent. On the contrary, normal vinilidene fluoroplastics does not exhibit dielectric unless it is rolled, and production is not easy.
In the present invention, the insulating layer comprises at least two layers, at least one of these layers is gel body having low hardness or viscous fluid, and an outer surface of the layer is coated with a second insulating layer having at least corrosion resistance.
Examples of the second insulating layer which can be used in the present invention are polyimide resin and fluoroplastics. Examples of the polyimide resin are not only all aromatic polyimide (PI) which is condensation reaction type and non thermoplastic non-thermoplastic, but also thermoplastic polyimide, polyether imide (PEI) and polyamide imide (PAI) which are additive reaction type thermoplastic polyimide. Examples of fluoroplastics are PTFE, PFA, ETFE and FEP, and PTFE and PFA, which are chemically stable, are especially preferable.
When the insulating layer is made of the synthetic resin material comprising the vinilidene fluoride as main component, it is preferable that its surface is further coated with PTFE (polytetrafluoroethylene resin layer) as the second insulating layer. In this case, it is especially effective when the plasma is used for working the semiconductor producing apparatus.
Meanwhile, it is possible to coat the electricity insulating layer comprising gel body with PFA, then coat the surface with PTFE or coat the electricity insulating layer comprising gel body with PTFE, subsequently coat the surface with polyimide resin to make three layer structure. In such a way, multi-layered structure, in which the anti-corrosive insulating layer is freely combined on the outermost layer, may be employed.
It is preferable that the thickness of the second insulating layer is thin in view of the contact thermal resistance, but if the thickness is too thin, the layer can not sufficiently function as a protecting film, and mechanical strength is also lowered. Especially when gel high polymer material of low hardness is used for the first insulating layer as in the static electricity chuck of the present invention, if the film thickness of the protecting film is 10 xcexcm or less, its strength cannot withstand the actual use, and at the same time, corrosion resistance becomes insufficient. On the other hand, if the film thickness exceeds 50 xcexcm, the hardness of the protecting film becomes high, the electricity insulating layer made of gel body does not deform as expected, the contact thermal resistance between the second insulating layer and the substrate becomes high, and heat transfer performance as expected cannot be obtained.
By optimizing hardness and resilience of the electricity insulating layer made of gel body and film thickness of the anti-corrosive second insulating layer coated with the said electricity insulating layer, it is possible to obtain high heat transfer performance, and to enhance the durability without deteriorating the cooling characteristics of the substrate.
While fluoroplastics other than polytetrafluoroethylene and other engineering resin are etched by ion, polytetrafluoroethylene, which has dielectric function, has small deviation of electron in molecule and thus, it is not etched by ion at the time of plasma etching. Nor it is not etched by radical. Further, normal polytetrafluoroethylene cannot be formed without sintering, and a defect such as pin hole is generated. The water dispersion type low molecular weight polytetrafluoroethylene resin has good adhesion with respect to vinilidene fluoroplastics, the melting point is low and thus, the pin hole is not generated. This low molecular weight polytetrafluoroethylene naturally has bonding uniformity with high molecular weight polytetrafluoroethylene of high melting point. Further, since it is not etched even under plasma atmosphere, it can be used for a long term.
Further, since it is possible to adjust the thermal deformation temperature by adjusting the molecular weight as described above, even if a surface of a parent material of the static electricity chuck comprising vinilidene fluoroplastics is coated with polytetrafluoroethylene resin, the following performance with respect to bumps and dips surfaces of the substrate is high, the film thickness is uniformly thin and thus, the heat transfer performance is not affected. Therefore, high heat transfer performance can be obtained between the holding stage of the static electricity chuck and the work piece substrate. Further, the polytetrafluoroethylene is crystalline, so separation performance with respect to the substrate is excellent.
It is preferable that a mixture layer of vinilidene fluoride and the polytetrafluoroethylene is disposed between the insulating layer and the outermost polytetrafluoroethylene layer, and its mixing ratio is sequentially reduced from the inner layer toward the outer layer.
For example, a mixing amount of resin made of vinilidene fluoride as main component with respect to the polytetrafluoroethylene on the side of the vinilidene fluoride which is the insulating layer is increased to secure the adhesion with respect to the parent material, the mixing amount is stepwisely reduced toward the outermost layer on the absorbing side of the static electricity chuck, and the copolymer comprising vinilidene fluoride as main component is set to zero and the copolymer is made of 100% polytetrafluoroethylene on the outermost layer.
If copolymerization ratio is stepwisely reduced toward the outer layer between the vinilidene fluoride side which is the insulating layer and the polytetrafluoroethylene layer which is the outermost layer in this manner, the adhesion of the resin layer interposed between the insulating layer made of resin comprising vinilidene fluoride as main component and the outermost polytetrafluoroethylene resin layer is secured. At the same time, by adjusting the copolymerization ratio, the melting point can also be adjusted. Therefore, sufficient following performance with respect to bumps and dips of the substrate to be processed can be obtained, and it is possible to reduce the contact resistance and to enhance the heat transfer performance.
Further, it is preferable that molecular weight of the polytetrafluoroethylene resin layer is stepwisely increased from a surface of said insulating layer toward the absorbing surface. For example, the polytetrafluoroethylene on the side of the vinilidene fluoride which is the insulative parent material is set to low molecular weight so that adhesion with respect to resin comprising vinilidene fluoride as main component is secured, and at the same time, the molecular weight of the polytetrafluoroethylene is gradually increased toward the absorbing side, such that the melting point is adjusted to a desired value. By adjusting the melting point, it is possible to obtain a static electricity chuck surface having excellent following performance with respect to bumps and dips of the substrate to be processed.
The water dispersion type low molecular weight vinilidene fluoride has excellent adhesion with respect to the vinilidene fluoroplastics and its melting point is low. Therefore, pin holes are hardly generated as compared with the vinilidene fluoroplastics. The adhesion between polytetrafluoroethylene having different molecular weights is also excellent naturally and thus, the layers are not peeled off from each other. In addition, since the layer is not etched even under plasma atmosphere, the layer can be used for a long term.
In the present invention, it is preferable that the third electricity insulating layer having high insulation is directly disposed on an upper surface of the metal support plate of the static electricity chuck, and the viscous fluid layer or gel body layer is sealed by the insulating layer and the anti-corrosion second insulating layer disposed the surface of the insulating layer. With this, the shape-keeping characteristics of the viscous fluid layer is secured, or it is possible to compensate a poor insulative portion of the gel body by the insulating layer directly disposed on the support plate. As the high insulating layer disposed on the support plate, various polyimide resin and fluoroplastics are used as in the anti-corrosive insulating layer.
It is preferable that the electrode is directly disposed on a lower surface of the second insulating layer having corrosion resistance, or the electrode is directly disposed on the upper surface of the third insulating layer having high insulating properties, on the support plate. By disposing the electrode on such a position, formation of various insulating layers is facilitated. The electrode can be fixed via adhesive on the lower surface of the second insulating layer or on the upper surface of the high-insulative third insulating layer on the support plate, but the electrode can also be formed directly by vapor deposition or the like.
Further, when the electrode is directly disposed on the lower surface of the second insulating layer, since the electrode approaches the substrate disposed on the upper surface of the chuck, the static electricity absorbing force is increased. When the electrode is directly disposed on the upper surface of the high-insulative third insulating layer on the support plate, the electrode is stably fixed, and function as an electrode can stably be obtained.
Moreover, it is preferable that the second insulating layer coats the other insulating layer and the outside exposing surface of the metal support plate on the periphery of the insulating layer, and when the insulating layer coating the outside exposing surface of the metal support plate is directly fixed on the support plate through adhesive, plasma resistance and etching resistance with respect to the adhesive are enhanced, and a static electricity chuck apparatus having excellent heat resistance, chemical resistance, and aging resistance can be obtained.
If the insulating layer coating the outside exposing surface of the metal support plate is polytetrafluoroethylene resin, since polytetrafluoroethylene resin is not etched by ion or radical in the plasma atmosphere, it is preferably applied to a static electricity chuck apparatus of a semiconductor producing apparatus using plasma. To effectively apply this characteristics to the semiconductor producing apparatus, it is preferable to coat, with polytetrafluoroethylene, not only a surface exposed to plasma of the static electricity chuck, but also the support stage which supports and holds the static electricity chuck and a portion of the peripheral device which is exposed to plasma. By coating such portions with polytetrafluoroethylene, it is possible to enhance the durability of the peripheral device and to elongate the life of the entire apparatus.